creat-react-app中的分包

'use strict';

const autoprefixer = require('autoprefixer');
const path = require('path');
const webpack = require('webpack');
const HtmlWebpackPlugin = require('html-webpack-plugin');
const ExtractTextPlugin = require('extract-text-webpack-plugin');
const ManifestPlugin = require('webpack-manifest-plugin');
const InterpolateHtmlPlugin = require('react-dev-utils/InterpolateHtmlPlugin');
const SWPrecacheWebpackPlugin = require('sw-precache-webpack-plugin');
const eslintFormatter = require('react-dev-utils/eslintFormatter');
const ModuleScopePlugin = require('react-dev-utils/ModuleScopePlugin');
const paths = require('./paths');
const getClientEnvironment = require('./env');

// Webpack uses `publicPath` to determine where the app is being served from.
// It requires a trailing slash, or the file assets will get an incorrect path.
const publicPath = paths.servedPath;
// Some apps do not use client-side routing with pushState.
// For these, "homepage" can be set to "." to enable relative asset paths.
const shouldUseRelativeAssetPaths = publicPath === './';
// Source maps are resource heavy and can cause out of memory issue for large source files.
const shouldUseSourceMap = process.env.GENERATE_SOURCEMAP !== 'false';
// `publicUrl` is just like `publicPath`, but we will provide it to our app
// as %PUBLIC_URL% in `index.html` and `process.env.PUBLIC_URL` in JavaScript.
// Omit trailing slash as %PUBLIC_URL%/xyz looks better than %PUBLIC_URL%xyz.
const publicUrl = publicPath.slice(0, -1);
// Get environment variables to inject into our app.
const env = getClientEnvironment(publicUrl);

// Assert this just to be safe.
// Development builds of React are slow and not intended for production.
if (env.stringified['process.env'].NODE_ENV !== '"production"') {
  throw new Error('Production builds must have NODE_ENV=production.');
}

// Note: defined here because it will be used more than once.
const cssFilename = 'static/css/[name].[contenthash:8].css';

// ExtractTextPlugin expects the build output to be flat.
// (See https://github.com/webpack-contrib/extract-text-webpack-plugin/issues/27)
// However, our output is structured with css, js and media folders.
// To have this structure working with relative paths, we have to use custom options.
const extractTextPluginOptions = shouldUseRelativeAssetPaths
  ? // Making sure that the publicPath goes back to to build folder.
    { publicPath: Array(cssFilename.split('/').length).join('../') }
  : {};

// This is the production configuration.
// It compiles slowly and is focused on producing a fast and minimal bundle.
// The development configuration is different and lives in a separate file.
module.exports = {
  // Don't attempt to continue if there are any errors.
  bail: true,
  // We generate sourcemaps in production. This is slow but gives good results.
  // You can exclude the *.map files from the build during deployment.
  devtool: shouldUseSourceMap ? 'source-map' : false,
  // In production, we only want to load the polyfills and the app code.
  entry: {
    // 'babel-polyfill': 'babel-polyfill',
    vendors: [ 'babel-polyfill','react', 'react-dom', 'react-redux', 'react-router', 'react-router-dom', 'redux', 'antd', 'antd-mobile'],
   'index': [require.resolve('./polyfills'), paths.appIndexJs]
    
  },
  output: {
    // The build folder.
    path: paths.appBuild,
    // Generated JS file names (with nested folders).
    // There will be one main bundle, and one file per asynchronous chunk.
    // We don't currently advertise code splitting but Webpack supports it.
    filename: 'static/js/[name].[chunkhash:8].js',
    chunkFilename: 'static/js/[name].[chunkhash:8].chunk.js',
    // We inferred the "public path" (such as / or /my-project) from homepage.
    publicPath: publicPath,
    // Point sourcemap entries to original disk location (format as URL on Windows)
    devtoolModuleFilenameTemplate: info =>
      path
        .relative(paths.appSrc, info.absoluteResourcePath)
        .replace(/\\/g, '/'),
  },
  resolve: {
    // This allows you to set a fallback for where Webpack should look for modules.
    // We placed these paths second because we want `node_modules` to "win"
    // if there are any conflicts. This matches Node resolution mechanism.
    // https://github.com/facebookincubator/create-react-app/issues/253
    modules: ['node_modules', paths.appNodeModules].concat(
      // It is guaranteed to exist because we tweak it in `env.js`
      process.env.NODE_PATH.split(path.delimiter).filter(Boolean)
    ),
    // These are the reasonable defaults supported by the Node ecosystem.
    // We also include JSX as a common component filename extension to support
    // some tools, although we do not recommend using it, see:
    // https://github.com/facebookincubator/create-react-app/issues/290
    // `web` extension prefixes have been added for better support
    // for React Native Web.
    extensions: ['.web.js', '.mjs', '.js', '.json', '.web.jsx', '.jsx'],
    alias: {
      // @remove-on-eject-begin
      // Resolve Babel runtime relative to react-scripts.
      // It usually still works on npm 3 without this but it would be
      // unfortunate to rely on, as react-scripts could be symlinked,
      // and thus babel-runtime might not be resolvable from the source.
      'babel-runtime': path.dirname(
        require.resolve('babel-runtime/package.json')
      ),
      // @remove-on-eject-end
      // Support React Native Web
      // https://www.smashingmagazine.com/2016/08/a-glimpse-into-the-future-with-react-native-for-web/
      'react-native': 'react-native-web',
    },
    plugins: [
      // Prevents users from importing files from outside of src/ (or node_modules/).
      // This often causes confusion because we only process files within src/ with babel.
      // To fix this, we prevent you from importing files out of src/ -- if you'd like to,
      // please link the files into your node_modules/ and let module-resolution kick in.
      // Make sure your source files are compiled, as they will not be processed in any way.
      new ModuleScopePlugin(paths.appSrc, [paths.appPackageJson]),
    ],
  },
  module: {
    strictExportPresence: true,
    rules: [
      // TODO: Disable require.ensure as it's not a standard language feature.
      // We are waiting for https://github.com/facebookincubator/create-react-app/issues/2176.
      // { parser: { requireEnsure: false } },

      // First, run the linter.
      // It's important to do this before Babel processes the JS.
      {
        test: /\.(js|jsx|mjs)$/,
        enforce: 'pre',
        use: [
          {
            options: {
              formatter: eslintFormatter,
              eslintPath: require.resolve('eslint'),
              // @remove-on-eject-begin
              // TODO: consider separate config for production,
              // e.g. to enable no-console and no-debugger only in production.
              baseConfig: {
                extends: [require.resolve('eslint-config-react-app')],
              },
              ignore: false,
              useEslintrc: false,
              // @remove-on-eject-end
            },
            loader: require.resolve('eslint-loader'),
          },
        ],
        include: paths.appSrc,
      },
      {
        // "oneOf" will traverse all following loaders until one will
        // match the requirements. When no loader matches it will fall
        // back to the "file" loader at the end of the loader list.
        oneOf: [
          // "url" loader works just like "file" loader but it also embeds
          // assets smaller than specified size as data URLs to avoid requests.
          {
            test: [/\.bmp$/, /\.gif$/, /\.jpe?g$/, /\.png$/],
            loader: require.resolve('url-loader'),
            options: {
              limit: 10000,
              name: 'static/media/[name].[hash:8].[ext]',
            },
          },
          // Process JS with Babel.
          {
            test: /\.(js|jsx|mjs)$/,
            include: paths.appSrc,
            loader: require.resolve('babel-loader'),
            options: {
              // @remove-on-eject-begin
              babelrc: false,
              presets: [require.resolve('babel-preset-react-app')],
              // @remove-on-eject-end
              compact: true,
            },
          },
          // The notation here is somewhat confusing.
          // "postcss" loader applies autoprefixer to our CSS.
          // "css" loader resolves paths in CSS and adds assets as dependencies.
          // "style" loader normally turns CSS into JS modules injecting <style>,
          // but unlike in development configuration, we do something different.
          // `ExtractTextPlugin` first applies the "postcss" and "css" loaders
          // (second argument), then grabs the result CSS and puts it into a
          // separate file in our build process. This way we actually ship
          // a single CSS file in production instead of JS code injecting <style>
          // tags. If you use code splitting, however, any async bundles will still
          // use the "style" loader inside the async code so CSS from them won't be
          // in the main CSS file.
          {
            test: /\.css$/,
            loader: ExtractTextPlugin.extract(
              Object.assign(
                {
                  fallback: {
                    loader: require.resolve('style-loader'),
                    options: {
                      hmr: false,
                    },
                  },
                  use: [
                    {
                      loader: require.resolve('css-loader'),
                      options: {
                        importLoaders: 1,
                        minimize: true,
                        // sourceMap: shouldUseSourceMap,
                      },
                    },
                    {
                      loader: require.resolve('postcss-loader'),
                      options: {
                        // Necessary for external CSS imports to work
                        // https://github.com/facebookincubator/create-react-app/issues/2677
                        ident: 'postcss',
                        plugins: () => [
                          require('postcss-flexbugs-fixes'),
                          autoprefixer({
                            browsers: [
                              '>1%',
                              'last 4 versions',
                              'Firefox ESR',
                              'not ie < 9', // React doesn't support IE8 anyway
                            ],
                            flexbox: 'no-2009',
                          }),
                        ],
                      },
                    },
                  ],
                },
                extractTextPluginOptions
              )
            ),
            // Note: this won't work without `new ExtractTextPlugin()` in `plugins`.
          },
          // "file" loader makes sure assets end up in the `build` folder.
          // When you `import` an asset, you get its filename.
          // This loader doesn't use a "test" so it will catch all modules
          // that fall through the other loaders.
          {
            loader: require.resolve('file-loader'),
            // Exclude `js` files to keep "css" loader working as it injects
            // it's runtime that would otherwise processed through "file" loader.
            // Also exclude `html` and `json` extensions so they get processed
            // by webpacks internal loaders.
            exclude: [/\.js$/, /\.html$/, /\.json$/],
            options: {
              name: 'static/media/[name].[hash:8].[ext]',
            },
          },
          // ** STOP ** Are you adding a new loader?
          // Make sure to add the new loader(s) before the "file" loader.
        ],
      },
    ],
  },
  plugins: [
    // Makes some environment variables available in index.html.
    // The public URL is available as %PUBLIC_URL% in index.html, e.g.:
    // <link rel="shortcut icon" href="%PUBLIC_URL%/favicon.ico">
    // In production, it will be an empty string unless you specify "homepage"
    // in `package.json`, in which case it will be the pathname of that URL.
    new InterpolateHtmlPlugin(env.raw),
    // Generates an `index.html` file with the <script> injected.
    new HtmlWebpackPlugin({
      inject: true,
      template: paths.appHtml,
      minify: {
        removeComments: true,
        collapseWhitespace: true,
        removeRedundantAttributes: true,
        useShortDoctype: true,
        removeEmptyAttributes: true,
        removeStyleLinkTypeAttributes: true,
        keepClosingSlash: true,
        minifyJS: true,
        minifyCSS: true,
        minifyURLs: true,
      },
    }),
    // Makes some environment variables available to the JS code, for example:
    // if (process.env.NODE_ENV === 'production') { ... }. See `./env.js`.
    // It is absolutely essential that NODE_ENV was set to production here.
    // Otherwise React will be compiled in the very slow development mode.
    new webpack.DefinePlugin(env.stringified),
    // Minify the code.
    new webpack.optimize.UglifyJsPlugin({
      compress: {
        warnings: false,
        // Disabled because of an issue with Uglify breaking seemingly valid code:
        // https://github.com/facebookincubator/create-react-app/issues/2376
        // Pending further investigation:
        // https://github.com/mishoo/UglifyJS2/issues/2011
        comparisons: false,
      },
      mangle: {
        safari10: true,
      },        
      output: {
        comments: false,
        // Turned on because emoji and regex is not minified properly using default
        // https://github.com/facebookincubator/create-react-app/issues/2488
        ascii_only: true,
      },
      // sourceMap: shouldUseSourceMap,
    }),
    // Note: this won't work without ExtractTextPlugin.extract(..) in `loaders`.
    new ExtractTextPlugin({
      filename: cssFilename,
    }),
    // Generate a manifest file which contains a mapping of all asset filenames
    // to their corresponding output file so that tools can pick it up without
    // having to parse `index.html`.
    new ManifestPlugin({
      fileName: 'asset-manifest.json',
    }),
    // Generate a service worker script that will precache, and keep up to date,
    // the HTML & assets that are part of the Webpack build.
    new SWPrecacheWebpackPlugin({
      // By default, a cache-busting query parameter is appended to requests
      // used to populate the caches, to ensure the responses are fresh.
      // If a URL is already hashed by Webpack, then there is no concern
      // about it being stale, and the cache-busting can be skipped.
      dontCacheBustUrlsMatching: /\.\w{8}\./,
      filename: 'service-worker.js',
      logger(message) {
        if (message.indexOf('Total precache size is') === 0) {
          // This message occurs for every build and is a bit too noisy.
          return;
        }
        if (message.indexOf('Skipping static resource') === 0) {
          // This message obscures real errors so we ignore it.
          // https://github.com/facebookincubator/create-react-app/issues/2612
          return;
        }
        console.log(message);
      },
      minify: true,
      // For unknown URLs, fallback to the index page
      navigateFallback: publicUrl + '/index.html',
      // Ignores URLs starting from /__ (useful for Firebase):
      // https://github.com/facebookincubator/create-react-app/issues/2237#issuecomment-302693219
      navigateFallbackWhitelist: [/^(?!\/__).*/],
      // Don't precache sourcemaps (they're large) and build asset manifest:
      staticFileGlobsIgnorePatterns: [/\.map$/, /asset-manifest\.json$/],
    }),
    // Moment.js is an extremely popular library that bundles large locale files
    // by default due to how Webpack interprets its code. This is a practical
    // solution that requires the user to opt into importing specific locales.
    // https://github.com/jmblog/how-to-optimize-momentjs-with-webpack
    // You can remove this if you don't use Moment.js:
    new webpack.IgnorePlugin(/^\.\/locale$/, /moment$/),

    new webpack.optimize.CommonsChunkPlugin({
      name: 'common',
      filename: 'static/js/common.[chunkhash:8].js',
      minChunks: 2  //三方库在逻辑代码中被调用两次(数字可以自定义)， 将公共的代码提取出来
    }),
  ],
  // Some libraries import Node modules but don't use them in the browser.
  // Tell Webpack to provide empty mocks for them so importing them works.
  node: {
    dgram: 'empty',
    fs: 'empty',
    net: 'empty',
    tls: 'empty',
    child_process: 'empty',
  },
};

将上述代码全部贴到node_modules文件下的react-scripts文件下的config文件下的webpack.config.prod.js中

以下是整理出的个人理解，有不懂的评论在一起讨论

一. 定义entry(入口文件)和output(出口文件)
二. 定义module(加载器: js、file、picture、css)
三. 定义resolve(配置模块如何解析)
四. 定义plugins(三方插件，主要有HtmlWebpackPlugin生成html插件、
	ExtractTextPlugin提取样式插件、
	CommonsChunkPlugin提取引用的第三方文件插件、
	UglifyJsPlugin压缩插件、
	DefinePlugin配置当前生产环境[后三个是webpack自带的])

1. 定义entry(入口文件)和output(出口文件)
    入口文件: 对应的是项目的入口文件
        * 一个入口起点： entry['index': path.join(__dirname, './src/index.js')]
        * 多个入口起点:  [分包必要]
            entry: {  //根据当前项目配置作说明
                'index': [require.resolve('./polyfills'), paths.appIndexJs],
                'babel-polyfill': 'babel-polyfill',
                vendors: ['react', 'react-dom', 'react-redux', 'react-router', 'react-router-dom', 'redux', 'antd', 'antd-mobile']
              },
    出口文件:  [分包必要]  
        output: {
            path: path.resolve(__dirname, './build'),  //打包输出的路径
            publicPath: '../',   // publicPath是打包的时候生成的文件链接（html文件）
            filename: 'js/[name].[chunkhash:8].js', //输出入口文件
            chunkFilename: 'js/[name].[chunkhash:8].js', //此选项决定了非入口chunk文件的名称
        },

2. 定义module(加载器) [分包必要]
    module.rules: 创建模块时，匹配请求的规则数组。这些规则能够修改模块的创建方式。这些规则能够对模块应用loader，或者修改解析器(parser)

    module: {
        //loaders加载器
        loaders: [
            {
                test: /\.js$/,                                  //用正则匹配文件类型
                exclude: /node_modules|picker.min.js/,          //排除特定条件
                loader: 'babel-loader',  //使用loader解析选项   //加载器
                options: {                                      //预设选项， 详细解释: https://webpack.docschina.org/configuration/modeule/#useentry
                    presets: ['es2015', 'react', 'stage-2']
                }
            },
            {
                test: /\.css$/,
                loader: ExtractTextPlugin.extract({     //三方插件
                    fallback: 'style-loader',			//编译过程中出现了错误，使用style-loader处理css
                    use: ['css-loader']                 //loader被用于将资源转换成一个CSS导出模块(默认使用css-loader编译css, “必填”)
                })
            },
            .
            .
            .
        ]
    }

3. 定义resolve: 打包模块时，webpack使用resolve来解析文件路径  [分包必要]
    1. resolve帮助webpack找到bundle中需要引用的模块代码，这些代码包含在每个require/import语句中
    2. 文件路径分为: 绝对路径[import "/home/me/file"]
		     相对路径[import "../home/file"]
		     模块路径[import "module/lib/file"]
    3. 配置解释:
        模块将在resolve.modules中指定的所有目录内搜索。 你可以替换初始模块路径，此替换路径通过使用resolve.alias配置选项来创建一个别名。

        一旦根据上述规则解析路径后，解析器(resolver)将检查路径是否指向文件或目录。如果路径指向一个文件：
            * 如果路径具有文件扩展名，则被直接将文件打包。
            * 否则，将使用[resolve.extensions]选项作为文件扩展名来解析，此选项告诉解析器在解析中能够接受哪些扩展名(例如 .js, .jsx)。

        如果路径指向一个文件夹，则采取以下步骤找到具有正确扩展名的正确文件：
            * 如果文件夹中包含package.json文件，则按照顺序查找resolve.mainFields配置选项中指定的字段。并且package.json中的第一个这样的字段确定文件路径。
            * 如果 package.json 文件不存在或者package.json文件中的main字段没有返回一个有效路径，则按照顺序查找resolve.mainFiles配置选项中指定的文件名，看是否能在import/require 目录下匹配到一个存在的文件名。
            * 文件扩展名通过 resolve.extensions 选项采用类似的方法进行解析。

        webpack 根据构建目标(build target)为这些选项提供了合理的默认配置。

4. 定义plugins
    主要做: 
    * 生成html文件 [分包必要]  //插件参数详情解释： https://segmentfault.com/a/1190000007294861
    举例：
        new HtmlWebpackPlugin({    //生成html文件
          template: './index.html',   //根据自己的指定的模板文件来生成特定的 html 文件
          inject: 'body',
          filename: 'js/index.html',   //输出html文件的位置
        }),

    * 将所有css文件抽取到一个文件中 [分包必要]
    举例:
        new ExtractTextPlugin("js/styles.css"), 
    注意: 抽取css文件，需要加载器配合，具体请看上边加载器

    * 用CommonsChunkPlugin提取引用的第三方文件插件 [分包必要]   //插件参数详情解释： https://segmentfault.com/q/1010000009070061

    * 压缩打包文件(防止打包后文件过大)[分包必要]   //插件参数详情解释：https://segmentfault.com/a/1190000008995453

    * 配置当前生产环境 [分包必要]

5. 正是环境不需要生成source-map文件[devtool: 'eval-source-map']




完整的分包案例请见: webpack.prod.conf.js
webpack官网：https://webpack.docschina.org

欢迎大家纠错。